This is the exact mirror, so Flashfreeze is good, but only against part of their deck. It counters red or green spells, so it hits their Hearth Elemental, Fiery Impulse, Prismari Charm and Traumatic Critique, plus sideboard cards like Colorstorm Stallion. It can't touch their mono-blue Eddymurk Crab, Sunderflock or Stormwing Entity, so hold it for the red spells and use it as a cheap tempo play. Stormwing Entity is a strong flying body that can come down cheaply after you've cast an instant or sorcery this turn. It survives a Fiery Impulse unless they have spell mastery, and it applies pressure their Eddymurk Crab can't block, though Sunderflock can. Winternight Stories is replaced because the mirror is about efficient tempo plays, not raw card advantage, and Get Out has few great targets against their similarly lean creature suite. Stubborn Denial can't counter creature spells, so use it to stop their noncreature spells such as Prismari Charm and Traumatic Critique, which protects your own Sunderflock and Eddymurk Crab, since the mirror often comes down to who lands their big Elemental first.